Binocular displays include head mounted displays such as glasses and helmet mounted displays wherein a virtual image is presented to each eye. The image, usually created by a microdisplay, for example an LCD screen, may be presented to the eye by means of refractive or reflective optics, for example, through a lens system. Ideally the virtual images presented to each eye are perfectly aligned and the user perceives a single image similar to their perception of real images. If the virtual images are misaligned, the user may experience discomfort, for example, eye strain, headache, and nausea.
Commercial binocular eyewear are aligned mechanically during manufacture and some misalignment is common. Furthermore, misalignment of binocular eyewear may occur during use due to physical shock or exposure to temperature or humidity. Although there are no widely accepted standards for alignment, there have been several studies to determine acceptable values of binocular image alignment. A compilation of the desired alignment tolerances to avoid user discomfort is as shown in the following table as disclosed in Melzer & Moffitt, Head Mounted Displays-Designing for the User, New York: McGraw-Hill, 1997 (ISBN 0070418195).
REQUIREMENTREQUIREMENTPARAMETER(see-through)(immersive)VERTICAL3 minutes of arc5 minutes of arcHORIZONTAL3 minutes divergent;¼ diopter of8 minutes convergentfocus distanceIMAGE ROTATION1 degree1 degreeMAGNIFICATION1 percent1 percentAlthough vendors of commercial eyewear displays are aware of the need for binocular image alignment, products today are not shipped with any alignment specifications.
Systems have been disclosed wherein a user of the binocular eyewear may take corrective steps to bring the misalignment within certain tolerances. See for example, in US 2003/0184860, the user operates a device to move a dot until it is aligned with another dot, and in WO 2006/058188, the user adjusts first and second display panels until images of display panel indicia shown on the viewing screen are located relative to baseline indicia.
However, users of systems requiring user intervention to properly align the system may find it burdensome to perform such intervention, especially when it may be required each time the system is turned on.
Accordingly, it is desirable to provide a method of aligning, without user interaction, the two images of a binocular eyewear display with respect to their vertical, horizontal, and rotational orientation, and with respect to magnification. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.